For my 20 long I have a seapora 60 running on a top find 1000 I've seen people recommend double filtration for planted tanks.
Should I get a more powerful pump or add an hob? Tank will have 6 females, 8 rummy nose tetra and some mts.

For planted tanks you don't neceserelly need extra filteration. Especially considering that your tank will not be over stocked bio load wise. The live plants will also absorb extra ammonia, and nitrites. I would Fishless cycle the tank before fully stocking it though. Will this tank be a Natural Planted Tank. Otherwise known as an NPT. If you would be doing this it will also reduce the water change schedule needed to maintain pristine water quality

That Is absolutely great as a matter of fact! You will definitely not need extra filteration with it being a NPT and (presumably) heavily planted with (presumably) 100% live plants. These would help with what the filter's main purpose is. To remove excess Ammonia and Nitrites which are harmful in high amounts and they also remove what the Beneficial Bacteria produces, Nitrates. Which are also Toxic in high amounts, I do not think you need anymore extra filteration